Navigational devices have been used with computers and other types of computing systems for many years. A computer mouse is one example of a navigation device. With a mechanical computer mouse, a ball rolls over a mouse pad as the mouse is moved. Interior to the mouse are wheels that contact the ball and covert its rotation into electrical signals representing orthogonal components of motion.
Another type of computer mouse is an optical mouse. FIG. 1 is a diagrammatic illustration of a portion of an optical mouse according to the prior art. Mouse 100 includes light source 102 and motion sensor 104. Light source 102 is typically implemented a light-emitting diode, which emits light 106 towards surface 108. Motion detector 104 typically includes a camera that captures images of surface 108. Motion detector 104 also includes a digital signal processor that receives and analyzes a sequence of images. Motion detector 104 determines the speed and distance mouse 100 has moved across surface 108 based on differences in the captured images.
The type and texture of surface 108 can impact how effectively motion detector 104 determines the speed and distance of mouse 100. For example, a rough or patterned surface can make it easier for motion detector 104 to determine the velocity of mouse 100, because differences in the images are more easily discernable. Other types of surfaces, such as glass surfaces, can make it more difficult for motion detector 104 to determine the velocity of mouse 100. Because glass is a transparent material, it typically does not have a sufficient amount of detectable imperfections or patterns that may be used to determine the speed and distance of navigation device 100.